Tomato - Enza Zaden

Tomato

guidelines

Production of tomatoes in tunnels

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the power of our tomatoes Marcel Mooij
the power of Enza Zaden Crop Breeding Manager Tomato

Sowing and transplanting

Sowing should be done in peat or substrate blocks for transplanting. Soil temperature during
germination should be 21-25°C. Air temperature can be 2-3°C lower. If the seedlings are
grown under artificial light, the level should be around 6.000 lux per m2 (standard in Holland).

The temperature at which the seedlings grow in the first few weeks, determines the number
of leaves that will be formed before the first fruit truss as well as internodes length. If it is
too high the plants will be more vegetative with more shooting. The intensity of the light also
affects the number of leaves - the higher the intensity, the higher the number of leaves.

Seedlings need a ‘cold treatment’ (temperatures at 16°C day and 14°C night for ten days) to
secure the setting of the first trusses starting from opening of the cotyledons to formation of
first true leaves. This also results in bigger cotyledons, thicker stems, short internodes, less
leaves on the main stem before the first truss and up to twice the number of flowers in the
first and second trusses.

At a lower temperature, split (branched) trusses will develop. The branching of the fruit
truss is influenced by the prevailing temperatures when the fruit truss is initiated. This is
a vegetative action. More flowers, but later flowering and smaller fruit size. Temperatures
below 15°C in cotyledon stage leads to less leaves till the trusses, later more leaves between
the trusses. A higher average temperature gives earlier harvest but lower yield. In low light
conditions the temperature should be lowered.
The seedlings should be potted at 2 true leaves. The bigger the pot, the better the seedling.

The plant will be ready for transplanting in about 30-35 days.

Planting period: E nd of April, production till August / September; aiming at 7-8 trusses.
Planting density: 2 ,5 - 3,0 plants/m² (for instance double rows with 60cm and 160cm

distance and 30-45cm in the row)

A higher plant density results normally in a more vegetative plant and a smaller fruit size.
Higher leaf-surface and the plant getting less light cause higher humidity in the greenhouse.
This makes the plant become more vegetative.

The standard plant density for (small) beef tomato is to start with 2,5 plants/m² and an
optional increase to a maximum 3,1 stems/m². A higher stem density than 3,1/m² normally
results in beef tomatoes with weak trusses and a small size.

With strong growing varieties it is advised to plant later with the first truss flowering. This is
a generative action, which forces the plant to use its energy at the fruits instead of vegetative
growth. Do not plant in too wet soil.

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Fruit setting

Due to low night and day temperatures as well as low light conditions, fruit may not set
properly in the beginning and the end of the crop. Fruits that do develop are small, seedless,
often pointed and worthless on the commercial market.

Good fruit setting takes place between 18-20°C (with a minimum generally accepted as
around 13ºC) and humidity at 60-70% RH. Pollination may still occur at day temperatures
of 35°C. As soon as the temperature drops below 9°C at night problems are encountered.
Setting goes easier in high light intensity and low light intensity.

To ensure the pollination of flowers at all times, the optimal is use of bumble bees to do
the job. If this is not possible, wires or strings of the trellis should be vibrated daily. Do this
preferably late in the morning to loosen the pollen and to allow it to drop on the stigma. This
is especially important in dark periods and can be done in a very simple way by hitting the
wires with a stick.

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Climate

The climate is influenced by the physical conditions (glass or plastic, low or high) in which the
tomatoes are grown, as well as the possibilities for heating, screening and ventilation. These
factors will directly influence temperature, humidity and light intensity.

The limitations in keeping the temperature down in the summer are much easier to influence.
Create extra possibilities to open for ventilation spread over the tunnel. Do not settle with just
a limited possibility to open in the ends. Important to remember is, that if you enter the tunnel
in the middle of a hot summer day and hardly can breathe in the heat, nor can the crop.

A too low night temperature (April, May) and too high day temperature (June, July) result in
weaker setting with loss of fruit quality and yield to follow.

The below temperature regime can be used as a guideline

From planting till 3rd truss flowers Rest of the crop

Morning 18°C 19°C
Afternoon
Night 20°C 21°C (+ 4°C degrees with sunny
weather between 13:00 and 15:00 hrs)

17°C 17°C

In a too vegetative crops the afternoon temperature can be kept an hour after sunset.

Though it may be difficult to regulate temperatures in a tunnel, it is still good to know the
influence of the temperature. We traditionally divide the 24h of a day in the following periods
(more modern climate computers in high-tech glasshouses have more periods):

Morning: Generally from sunrise until 11:00 – 12:00 o’clock.

Afternoon: Generally from 12:00 o’clock until sunset (in spring).

Pre-night: Generally from sunset for a period of 3-4 hours (in general not possible/difficult

to keep a pre-night temperature from May onwards in continental climates,

due to higher outside temperatures).

Night: Period after pre-nigh until sunrise.

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Climate

Morning

Cooler morning temperatures (for example 17°C) result in shorter internode length, more
vigorous/dense plants and stronger trusses. It is important that the morning temperature is
reached at sunrise. This prevents condensation on the larger fruits and activates the plant
(transpiration). This also decreases the amount of king fruits. Higher temperatures in the
morning tend to have the effect to stretch the plant (longer internodes) and make the truss
stem longer.

Afternoon

The afternoon is normally the period of the day with the highest radiation and as a result
also the highest photosynthetic activity. Temperature, together with CO2 level and sunlight
are the most important factors of photosynthetic activity. That’s why in the afternoon the
highest temperature is kept in the greenhouse. Often a light increase is used between 13:00
and 15:00 hrs in springtime. That means that the temperature is increased on sunny days, for
example with between 1°C and a maximum of 4°C, depending on the radiation level.
The use of higher afternoon temperatures and a light increase are generative actions.

Pre-night

The pre-night is normally the period with the lowest temperatures in the greenhouse. A pre-
night is mainly used to increase the size of the fruits. For the pre-night to have the desired
effect it is important that the pre-night temperature is reached as soon as possible after
sunset. A lower pre-night temperature results in larger fruit size and increases the fruit load.
The use of a pre-night is a generative action.

Night

The night temperature has an impact on 24h average temperature and, of course, the day
and night temperature difference. Low night temperatures in combination with a long
after sunrise (morning set point temperature is reached too late) can cause fruits with a
large blossom end scar (cat face). This results in a high humidity in the greenhouse and
consequently inactive plants in the morning.

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Climate

24 hour average temperature

The general rule is, the higher the average 24h temperature is, the more generative is the
climate. Higher 24h averages increases the speed of truss development.

Difference between day- and night temperature

The general rule is: the larger the difference between day- and night temperature, the more
generative the climate is.

Example of generative climate set point

Morning: 19°C

Afternoon: 21°C, with a light increase until a maximum temperature of 25°C between 13:00

and 15:00 hrs, depending on the radiation.

Pre-night: 15°C (go to the pre-night temperature at sunset).

Night: period: 17°C.

This is a generative set point, because:

• The use of a light increase and a lower pre-night result in a larger difference between day

and night.

• The 24h temperature increases, due the use of a light increase and the use of a higher

morning temperature.

Example of vegetative climate

Morning: 18°C.

Afternoon: 20°C (no light increase).

Pre-night: 16°C (go to the pre-night temperature 1 hour before sunset).

Night: 17°C.

This is a vegetative set point, because there is only a small difference between day and night
temperature.

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Climate

Common climate actions taken when the crop is too vegetative in spring
time
• Use a substantial light increase (for example 4°C) in the afternoon (only on sunny days).
• Keep the afternoon temperature one hour longer (in the example above 21°C until 1 hour

after sunset).
The actions mentioned above result in higher 24h average temperature

Common climate actions taken when the crop is too generative in spring
time
• Stop using a light increase in the afternoon. Try to keep the afternoon temperature only

1 or 2°C higher than the morning temperature.

• Go a bit earlier to the pre-night temperature (for example 1 hour before sunset).
• Use a small temperature difference between day and night.

The actions mentioned above result in a lower 24h average temperature.

Energy requirement of the plant

General rule is that a plant needs around 125 joules per truss (depending on the type) and
another 100 joules for plant itself. That means that a small beef variety where the 4th truss
is flowering needs around 600 joules (4 x 125 joules + 100 Joules) a day. In January and
February it can happen that the light levels are for a longer period less than the requirement
of the plant. In such a situation, the only option is to decrease the 24h average temperature
(reduce the energy requirement of the plant). This of course has a negative impact on the
truss development speed. Too high temperatures in periods with low light levels can lead to
the abortion of the complete truss.

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Head thickness

The thickness of the head is a good indicator of the condition of the crop. A stem thickness
between 10,5 and 11mm is ideal. When the stem thickness increases to more than 11,5mm, it
is normally a sign that the crop becomes too vegetative. When the stem thickness decreases
to less than 10mm, it is normally a sign that the crop becomes too generative.

Irrigation

The importance of water is obvious, but especially during the stage of fruit development the
demand is high. At the beginning it is advised to irrigate with slightly less water in order to
allow the plant to develop more roots (let him search for water).
It is recommended to irrigate with a dripping system to avoid a wet crop, risking various foliar
disease problems. As a guideline: the need in the beginning will be 1,5-2,0 liter/m² increasing
to 3-6 liter/m² in the summer. Important is to follow the development of the crop, the soil type
and the weather conditions.
Attention to climatically changes is required. Too abundant watering can cause root damage.
This can even lead to death and wilting of the plants, especially during cloudy humid days or
at the periods when days become shorter. Covering the soil with white plastic helps on two
sides: the light intensity increases and the humidity is lowered. Too wet soil and too much N
is a vegetative action.
If the crop is grown in substrate, the general rule in spring and summer for the amount of
water is radiation (joules) x between 3 and 4 = cc/m2 (depending on the tomato type, use of
rootstock and condition of the crop). Another thing is that it is important to have sufficient
drain in the afternoon (from 12:00h onwards), 30% is normal set point and that the water
content of the substrate doesn’t drop more than 10% during the night.

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Fertilization in soil crops

A proper fertilization should be based on the basic information from a soil analysis (EC, pH,
N, P, K, Ca, Mg) and the condition of the crop. The following recommendations are made as a
general guideline for the growers using drip irrigation systems. Local conditions (climate, soil
type, fertilizers, water quality etc.) are important factors that will influent the crop.

N-min measured value should be:

• Beginning of May 95Kg N/Ha (0 - 30cm).
• End of June 140Kg N/Ha (0 - 30cm).
• End of July 165Kg N/Ha (0 - 60cm).

As the growing conditions for tomatoes under none climatically controlled circumstances are
very difficult to influence (temperatures, humidity, soil type, and water quality) it is important
to arrange a type of buffer in order to allow the plant to uptake nutrition as easy as possible.
This can be obtained by organic manure 25-35 tons/ha. Important is to incorporate the
manure early enough, watering it frequently in order to allow sufficient nutrition in time. It
is also very important that the manure is well fermented in order to prevent burning of the
plants due to the production of heat by the manure.

The manure should release nutrients quickly when necessary, and should contain as little as
possible salts (sodium, chloride). The best manure is from cattle. Chicken manure can damage
the crop as it is rich with Urea. Sheep manure is usually more salty, and deliberates too slow
for the plant.

The advised N and K level in irrigation is around N 15mmol/L and K 8mmol/L. Give more
potassium in the beginning and in the autumn. Remember the micro/trace elements.

Advisable EC level at crop fertilisation is 2–2,5 mS/cm, or concentration 0,15-0,2%.
Advisable pH level is 6-6,5. Use nitric acid (HNO3) if the pH is too high (over 7).

Give calcium weekly, separately from the other fertilisers, due to the chemical incompatibility.
Don’t mix the phosphates and nitrates in the basic solutions.

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Furtilization in soil crops

Example advice for Belle

Protected crop, yield 150t/ha

Timing Fertilizer [Kg] Needs In Kg
N
Total uptake Multi Comp 14/13/20 + 2 1000 400 P2O5 K2O MgO CaO
Base dressing 140 220 600 80 90
Fertilization plan Polyfeed 11/44/11+ME 50 130 200 20
2 weeks after 150 100
planting Polyfeed 21/11/21+ME 300 5,5 22 5,5 1
Till fruit setting 5 Polyfeed 16/8/32+ME 650 16,5 31,5 3
weeks Multi K 12/0/42+2 400 31,5 24 96 6
Multi Cal 15,5/0/0/25,5 200 48 0 273 13
Harvesting period Magnisal 11/0/0/+16MgO 100 78
(16 weeks) Polyfeed 11/44/11+ME 64 0 0 32
Microelements 22 44 11 2
Every 14 days 11
during harvesting

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Fertilization in substrate crops

A higher EC in the substrate makes it more difficult for the plant to take up water and
nutrients and is consequently a generative action. A higher EC results in a darker leaf colour,
more generative plant and has a positive effect on the fruit quality and taste. Especially in the
first months of the crop the EC is a good tool to control vegetative growth. In general an EC
between 4 and 5 is preferred in the substrate throughout the season.

Example of a generative fertilization strategy
• Fill the substrate with an EC between 3,8 and 4.
• Use a drip EC between 3,5 and 3,7 in the first three months of the crop.
• From the end of April onwards reduce the drip EC gradually to and EC between 3,0 and

3,2. This helps the plant to up take water and nutrients easier in summer time.

• Increase the drip EC again to 3,5 after taking out the top.

Further it is important to increase the Boron level of the drip water to 250μmol/l instead of the
standard 70μmol/l. A higher Boron level reduces fruit fall.
Keep higher concentration and higher Potassium ratio at low light condition (overcast
weather), and in the autumn crop as well. Remember the micro/trace elements.
After a pickling crop, in general the nitrogen level in the substrate is quite high for which
reason it is advisable to use a bit lower N level than normal at the start of the crop.

CO² management

If CO² can be supplied; a level of 500-700ppm will be optimal. By lots of light on a sunny day,
it can be increased till max 1.000ppm.

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Furtilization in substrate crops

Fertilizer deficiency symptoms

It is strongly advised to make soil analysis along the season to check the contents of fertilizers
available for the plants. Yet, it is useful to know some of the signs at deficiencies.

Iron: iron deficiency is first to be seen in the top. The leaves turn yellowish while the leaf

nerves stay green. This deficiency often occurs when the PH is too high or when the
soil structure is too bad. At short notice the deficiency can be helped with Iron-chelate
treatments. At long term soil structure should be improved.
Boron: the shoot tips cripple, flowers or even fruits drop off, fruit cracks and the root
development decrease. This deficiency is mainly seen at strong soil and at high PH level. It is
a need to look into the trace elements / micro fertilization and to supply 10 – 20kg/ha Borax.
At long term soil structure needs to be improved.
Magnesium: the leaves yellowish from the edge while the nerves and the surrounding tissue
stays green. The leaves are often thicker than normally and give a ‘crispy’ impression. This is
caused by a too low Ph level and a too high potassium level. To prevent this, the potassium
level needs to be balanced. At short notice you can spray with a 0,5-1% Magnesium-sulphate
solution. At longer term ad Magnesium -Sulphate 500Kg/Ha.
Calcium: calcium deficiency or Blossom End-rod is a brown, haggard spot at the fruit where
the flower is or has been attached. Normally this is not caused by an undersupply of calcium
in the soil but entirely by the availability in the plant. Calcium is not easily transported in the
plant and only by an active ascent of sap in the plant. During periods with high humidity and
low transpiration, the sap transport to the parts of the plants long away from the roots (as
flowers and fruits) is less. The problem is increased by a high EC. Prevention takes place by
supporting the transpiration by ventilating more and securing a decent water supply.

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Furtilization in substrate crops

Excessive applications of nitrogen and potassium
Nitrogen
• Large hollow fruit.
• Bigger plants.
• Excessive vegetation.
• Soft fruit.
• Blotchy ripening (associated with too narrow N:K ratio).
• Increase of yield, but at expense of quality.
Potassium
• Regular plants with limited vegetation.
• Small to regular fruit.
• Firm, long shelf life fruit.
• Good colour and flavour.
• Loss of yield.

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Physiological fruit disorders Cracking and yellow shoulders
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Cracking

Concentric cracking or radial cracking can occur.

Cause

• Too much N, too little K.
• Very fast fruit growth.
• Irregular irrigation.
• Wide fluctuations in day and night temperatures for prolonged periods.
• High humidity.
• Excess de-leafing.
• Some varieties more susceptible.

Control

• Proper water management.
• Good fertilising program.
• Proper pruning and leaf defoliation.
• Shading under high temperatures and radiation.
• Good plant protection to prevent disease and control pests on time.
• Choose the right variety.

Yellow Shoulders

Affects the shoulders of tomato fruit exposed to high temperatures during ripening. The
shoulder either remains green or turns yellow. At high temperatures the main pigment in the
fruit skin remains carotinoids (yellow/orange) while Lycopene, the red pigment, is largely not
metabolised.

Control

• Proper nutrition and irrigation.
• Avoid excessive pruning and defoliation.
• Avoid foliage diseases.

Gold Speckles

Yellow speckles (calciumoxalat crystals) are formed under the fruit skin due to a too high
humidity.

Control

• Ventilate to lower the humidity.

Physiological fruit disorders

Blossom end rot Blossom end rot
Blossom end rot
Blossom end rot symptoms are light brown water soaked lesions, which turn black and
leathery. You usually get it on the blossom end of the fruit and on that black mould becomes
a secondary infection.

Cause

• Localised Ca deficiency in the blossom point of the fruit. Ca does not move easily within

the plant self.

• Fluctuations in the water supply will dilute the amount of Ca.
• High soil salinity also prevents Ca getting through.
• Use of ammonium nitrate also competes with the other cautions, decreasing the pH of

the soil.

• High relative humidity.
• During hot dry weather if plants have root damage then they will have a problem of Ca

absorption.

• Reduction or stop of the transpiration stream during midday (heat, salinity etc.).

Control

• Correct fertilisation and water control.
• Applying lime 2-4 months before planting can help a lot.
• Avoid soil with high salinity.
• Reduce salinity – ensure enough leaching of unwanted or high salts out of medium.

Blotchy Ripening

Physiological disorder. Appearing only in ripened fruit and never in green stages. Usually it
occurs only on lower trusses.

Cause

• Lack of K (and/or Ca).
• Large temperature variations over the 24-hours day.

Control

• As soon as it appears use low N and high K mixtures.
• As fruit quality improves return to normal feed.

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Physiological fruit disorders

Cat face

Cause

• The problem can occur during blossoming.
• Sometimes it also happens in hot weather.
• Herbicides can cause it as a drift from other neighbouring crops.
• Excessive levels of nitrogen increase the problem.

Control

• Proper irrigation and nutrition.
• Temperature management.
• Certain varieties are more susceptible to cat facing than others.

Puffiness / hollow fruit

Both problems go together. Puffiness occurs when the fruit has an angular boxy appearance.
A cavity is present between the outer wall and the locular content. Incomplete locular
development with very few seeds and little juice are the result. The fruit will float in water.

Cause

• Inadequate pollination, fertilisation or seed development.
• Improper nutrition.
• Insufficient light.
• Low or high temperature fluctuations.
• Excess of water.

Soft Fruits

The fruits loose firmness and become soft. This happens especially in a warm summer period.

Control

• There can be differences between varieties.
• Very often soft fruits appear when the crop is pushed too hard. An early variety is more

susceptive as a later variety.

• It can be limited by ventilating at 23-24°C.
• Allow some heat at the bottom pipes in the house during night and also the EC has effect.
• Do not irrigate with clean water; always have some fertilizer along with the water to keep

sufficient EC level.

Blotchy Ripening

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Pruning Most modern tomato hybrids have a strong vigour and fast plant development. In order to get
Harvesting good fruit quality and large size, it is important to create a plant with a good balance between
vegetative and generative growth. Side shoots use more energy than they produce and must
be removed as soon as possible.

It is recommended to de-leave the plants when the 4th or 5th cluster is flowering. The first
3 bottom leafs can be removed then. Air-movement and light penetration will improve,
which has positive effects on fruit size and quality. The open crop is also less susceptible
for Botrytis. When the 7th truss flowers, leafs can be taken of till the first truss. As the crop
grows, de-leaving continues normally to the truss where fruits are colouring.

Be aware that if removed leaves are left at the ground and stay wet, the fermentation can
result in Ethylene which can lead to lower keep ability of fruits.

A good tool to create a more open en generative plant habit with vegetative varieties is to
take out a top leaf behind the flowering cluster, when twisting the plants (ones a week).
Depending on the condition of the crop, it is common to start taking out a top leaf when the
third truss is flowering and stop no later than the end of April, to ensure that the plants have
enough vigour to get through the summer. This improves light penetration early in the season
and contributes to a more generative plant growth.

Mid August plants should be topped and non-pollinated fruit removed.

Ideal maturity for harvested fruit depends on time of season and if they are to be
transported/exported or meant for the local market. In the summer the fruits should be picked
when the bottom tip of the tomatoes have an orange-pink tint. The fruit will turn a light red
within 2-3 days. They will keep well for at least 7 days at normal shop temperatures. Early and
late in the season, when maturing goes slower, the fruits should be harvested when orange.
For the local market they should be more matured. High temperature during ripening results
in less lycopene/red colour.

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Resistances

Resistances in varieties of our crops will be coded (see for High resistance (HR) - plant varieties that highly restrict the growth
explanation our coding list at www.enzazaden.com.), unless and development of the specified pest or pathogen under normal
indicated otherwise. In case a variety is resistant to more than one pest or pathogen pressure when compared to susceptible varieties.
pathogen, the individual resistance codes will be separated by the These plant varieties may, however, exhibit some symptoms or
symbol “/”. damage under heavy pest or pathogen pressure.

• If in a resistance code of a certain variety reference is made to Intermediate resistance (IR) - plant varieties that restrict the growth
certain strains for which the resistance is claimed this means that no and development of the specified pest or pathogen, but may exhibit
resistance is claimed to other strains of the same pathogen. a greater range of symptoms or damage compared to highly resistant
plant varieties. Intermediate resistant plant varieties will still show
• If in a resistance code no reference is made to strains of the less severe symptoms or damage than susceptible plant varieties
pathogen for which the resistance is claimed this means that when grown under similar environmental conditions and/or pest or
resistance is claimed only to certain not further specified strains of pathogen pressure.
the pathogen and herewith disclaiming any guarantee that the variety
will not be infected by the said pathogen. Tolerance (T) - the ability of a plant variety to endure abiotic stress
without serious consequences for growth, appearance and yield.

Disclaimer

Descriptions, recommendations and illustrations in brochures and leaflets shall correspond as closely as possible to tests and practical
experience and are subject to typographical and/or printing errors. This information shall be provided to assist professional growers and
users, whereby variable local conditions must be taken into account. Under no circumstances shall Enza Zaden accept liability based on such
information for deviating results in the cultivated product. Current information concerning the resistances is available on
www.enzazaden.com.

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enzazaden.com

Enza Zaden Export B.V.

Postbus 7 | 1600 AA Enkhuizen | the Netherlands
Haling 1E | 1602 DB Enkhuizen | the Netherlands
tel +31 (0)228 35 01 00 | fax +31 (0)228 35 02 00
[email protected] | www.enzazaden.com

Descriptions, recommendations and illustrations in brochures and leaflets shall correspond as closely as possible to tests and practical experience and are subject to typographical and/or
printing errors. This information shall be provided to assist professional growers and users, whereby variable local conditions must be taken into account. Under no circumstances shall
Enza Zaden accept liability based on such information for deviating results in the cultivated product. Current information concerning the resistances is available on www.enzazaden.com.
© Enza Zaden Export B.V. | Enkhuizen | The Netherlands | March 2014